Air filter systems for debris collecting apparatus

ABSTRACT

A mobile debris collecting device including a vehicle mounted debris box with an entrance for air-carried debris and a clean air flow exit, the box having an internal division and including, in separate compartments, a bag house filtering unit and a cyclone filtering unit, the units being usable separately from one another.

1 1 Mar. 11, 1975 Ruble et a1. Wendel United, States Patent Shaddock55/314 X 55/302 55/315 55/432 X 55/337 X Shaddocli..................

Stephens.......,............ Kluge etCornett.............................

ABSTRACT 4 Claims, 6 Drawing Figures (FMHHHH I I i114,

Primary ExaminerTim R. Miles Assistant ExaminerNeil F. GreenblumAttorney, Agent, or Firm-1-1ill, Gross, Simpson, Van Santen, Steadman,Chiara & Simpson A mobile debris collecting device including a vehiclemounted debris box with an entrance for air-carried debris and a cleanair flow exit, the box having an internal division and including, inseparate compartments, a bag house filtering unit and a cyclonefiltering unit, the units being usable separately from one another.

[ AIR FILTER SYSTEMS FOR DEBRIS COLLECTING APPARATUS [75] Inventor:Roland E. Shaddock, Streator, 111.

[73] Assignee: Myers-Sherman Company, Streator,

| l ih l l i l i lr ll 1h N J IHH il N H" H Int. B0ld 50/00 Oct. 13,1972 References Cited UNlTED STATES PATENTS 3/1942 Tolman,

[22] Filed:

[2]] Appl. No.: 297,408

[58] Field of Search 1 FATENTEDHAM 119. 5

Szi-LET 2 U? 3 mm mm. mm 2 PATENIEB MRI 1 I975 SHEU 3 OF 3 AIR FILTERSYSTEMS FOR DEBRIS COLLECTING APPARATUS BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to debr is collectingapparatus and more particularly to an air-filter system having dualcapabilities for such apparatus.

2. Prior Art Air-filtering systems used separating debris from anair-stream are well known. Two commonly used types are bag houses-andcyclones.

It has also been known to mount air-filtering systems on vehicles formobile debris collection. Such mobile systems generally include avehicle carrier equipped with a debris collecting box containinginteriorly thereof the air-filtering system. The box generally has aseparate inlet and a separate outlet, the inlet being connected to acollection hose and the outlet being connected to the primary air flowinducer such as a fan, compressor, or the like.

The air flow through such a system is from the collec tion hose to theinterior of the debris box and then through the filter system to theoutlet from the box to the primary air flow inducer.

The type of air filter system to be used is determined by the type ofdebris to be collected. For example where the debris to be collectedconsists ofa fine sized particle matter such as a dust, fly ash, rockdust, or talclike material, and particularly in those instances wherethe debris is dry, a bag house provides the best filtration. Howeverwhere larger size particles or where wet material, such as leaves andthe like material is to be collected, a cyclone type of filtering systemis preferable. Heretofore, the art has provided only a single filteringsystem mounted on a single vehicle. This is not proved disadvantageouswhere the use of the vehicle is to be limited to a given type of debriscollection. However where a general use vehicle is desired, it hasgenerally been necessary either to use two separate vehicles equippedwith differing filtering systems or to change the filtering systemwithin the vehicle depending upon the nature of the debris to becollected by the apparatus. It would be an advance in the art to providea single debris collecting apparatus equipped with both wet and dryfiltering systems. it would be further an advance in the art if such anapparatus could be provided wherein the filtering systems can be usedseparately from one another.

SUMMARY My invention provides a single debris collecting apparatus,which may be, and in the preferred embodiment is, vehicle mounted andwhich includes both wet and dry air-filter systems usable separatelyfrom one another. This system includes a debris box which has disposedinteriorly thereof both a cyclone air-filter system and a bag houseair-filter system, the systems being positioned in separate internalcompartments. Means are provided for using the filter systemsindependently of one another.

'In the preferred embodiment the debris collection box consists of a sixsided rectangular, hollow box which has a transverse internal divisionwall therein. The internal division wall is preferably double hulled,with on hull extending from the top of the box and terminating in'spacedrelation to the bottom of the box and the other hull extending from thebottom of the box and terminating in spaced relation of the top of thebox. The wall is located closer to the front than to the rear of the boxwith the rearmost hull of the wall terminating in spaced relation to thetop. A bag house assembly is positioned between the front wall of thebox and the transverse wall. A cyclone filter system is positionedbetween the rear of the transverse wall and the rear of the box. Thedebris collection hose communicates with an inlet to the debris boxwhich extends from the front of the box past the transverse wall intothe rear compartment. The cyclone filter system has a closable openingthereto and the transverse wall has a closable opening between the topof the rearmost hull and the top of the box. Both the cyclone and thebag house filtering systems exhaust to a common outlet from the debrisbox. The common outlet is in turn connected to a primary air flowinducer.

in the preferred embodiment, positioned below the bag house are a pairof transverse angers adapted to move material filtered from the airstream by the bag house to the side of the forward compartment. Thetransverse augers terminate above the end of an angled elevating augerwhich moves the debris to the rear compartment through the transversewall for storage therein. In this manner it is not necessary to emptythe forward compartment containing the bag house when dumping the debrisbox. A closure plate is provided at the terminus of the angled auger.

Thus, when it is desired to use the cyclone system, the closure plate atthe terminus of the angled auger is positioned to close offcommunication through the angled auger housing and the closure platebetween the top of the debris box and the top of the rearmost hull ofthe transverse wall is positioned to block off communication between thefront and rear compartments of the debris box. Further, the closureplate at the opening to the cyclone unit opened. Thus, the debrisentering the debris box through the inlet flow with the. air stream tothe rear compartment where the heavier particles will fall out. The air.stream and the remaining debris flow into the cyclone filtering unitwhere the debris are removed in a known manner from the air stream. Theair stream then passes through a transverse duct to another duct whichin turn communicates to the common outlet.

When it is desired to use the bag house, the closure plate at theentrance to the cyclone filtering system is closed and the closureplates at the terminus end of the angled auger end at the rearmost hullof the transverse wall are open. The air flow is then from thecollection hose through the entrance duct to the rear compartment andthen through the double hulled wall to the front compartment, thenthrough the bag house to a duct connecting to the outlet.

The debris separated from the air stream by the bag house filter systemfall to the bottom of the front compartment where they are moved by thetransverse augers to the angled auger. The angled auger then moves thedebris to the rear compartment for eventual dis posal.

Because of the provision of the dual air filtering systems in the singledebris box, the versatility of the debris collecting apparatus is vastlyincreased. In addition, the provision of the separate internalcompartments allows the use of one of the air filtering systemsindependently of the other.

It is therefore an object of this invention to provide an improveddebris collecting apparatus.

It is another, and more specific object of this invention to provide adual air filter system debris collecting apparatus.

It is a more specific object of this invention to provide a debriscollection apparatus using a flowing air stream to collect debris and todirect the debris to the interior of a debris box, the debris box havingan air filtering system therein to remove the debris from the air streamand the debris box being equipped with two separate air filteringsystems.

It is yet another and more specific object of this invention to providea debris collecting apparatus having a debris collecting box with twoair filter systems disposed therein in separable compartments with oneof the air filter systems being a cyclone filter system and the otherbeing a bag house filtering system and means being provided to operatethe systems independently of one another for the filtering of an airstream flowing through the said debris box.

It is yet another and most specific object of this invention to providea mobile debris collection apparatus having a vehicle mounted debris boxwith an air flow induced therethrough, the air flow entering the debrisbox from a debris collection hose and passing through an internal airfilter system whereby the air stream exits the box clean of the debris,the box containing two air filter systems in separable compartments, theair filter systems being usable one at a time, and the air filtersystems being adopted to remove different types of debris from the airstream.

' BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features andadvantages of the invention will be readily apparent from the followingdescription of a certain embodiment thereof, taken in conjunction withthe accompanying drawings, although variations and modifications may beeffected without departing from the spirit and scope of the novelconcepts of the disclosure, and in which:

FIG. 1 is a perspective view of a mobile debris collecting apparatushaving a debris collection box equipped with the air filtering systemsaccording to this invention;

FIG. 2 is a perspective view of the debris collection box illustratingthe placement of the internal components thereof by broken lines;

FIG. 3 is a side view partially in section of the debris collection boxof FIG. 2;

FIG. 4 on page 3 of the drawings, is a view taken along the line 4-4 ofFIG. 3 illustrating the interior of the debris collection box;

FIG. 5 on page 2 of the drawings, is a part sectional view of thetransverse wall of the debris collection box;

FIG. 6 on page 2 of the drawings, is a fragmentary sectional view of thedebris box of this invention taken generally along the line 4-4 of FIG.4.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a mobiledebris collecting apparatus 10, consisting of a vehicle 11, having aframe 12 on which is mounted a debris collection box 13, an auxiliarypower source 14, a debris collection hose and a primary air flow inducer16, which may be a fan or compressor, or the like.

In the preferred embodiment, the debris collection box 13 is hinged fordumping from the rear and the debris collection hose 15 connects with aninlet 18 to the box located at the front of the debris collection box,the connection being through a severable connection 19. The primary airflow inducer 16 connects with an outlet 20 from the debris collectionbox through a severable connection 21.

In operation, the auxiliary power source 14 operates the air fiowinducer 16 to induce a flow of air from the debris collection end 22 ofthe hose 15 through the inlet 18 to the debris box through an airfiltering system positioned within the debris box. The air flow thenexits the box through the outlet 20 into the air flow inducer 16. Theair stream is then discharged to the atmosphere.

The debris box, best illustrated in FIGS. 2 and 3, has its interiordivided into forward 25 and rear 26 compartments. In the preferredembodiment, the debris box is constructed of outer 27 and inner 28walls, separated by I-beams 29, the I-beams defining channels across thewidth of the debris box on the top and bottom thereof and, definingvertical channels at the front and rear and along the sides. The spaces30, defined between the beams and the outer 27 and inner 28, walls canbe used for air flow purposes as hereinafter described.

Positioned intermediate the front 31 and rear 32 walls of the debris boxis a transverse dividing wall 33 which divides the debris box into thecompartments 25 and 26. In the preferred embodiment the wall 33 ispositioned forward of the center line of the debris box. Wall 33consists of a double hull wall having a rear wall or hull 34 and a frontwall or hull 35 separated by spaced apart vertical beams 36. The rearwall 34 begins in contact with the inner bottom wall 28a of the floor ofthe debris box and extends upward, terminating at an end 38 in spacedrelation to the inner wall 28 of the top of the debris box. The forwardhull 35 of the wall 33 being in contact with the inner wall 28 of thetop of the debris box and extends downwardly and terminates at a point40 in spaced relation to the inner wall 28a of the bottom of the debrisbox. In this way communication is provided between the two compartments,the communication being the pathway between the points 38 and the innerwall 28 through the vertical channels defined between the beams 36 andfrom the channels to the forward compartment 25 and between the point 40and the bottom inner wall 28a of the debris box.

As illustrated in FIGS. 2 and 6, the transverse wall 33 is pierced by aduct 42 which also pierces the front wall 31 of the box 13 and connectsto the inlet opening 18. The duct 42 extends into the rear compartmentat 26 and terminates in an open end 43. Positioned within the rearcompartment, as best illustrated in FIGS. 2, 3 and 4, is a cyclone airfiltering system 45. In the preferred embodiment two cyclones 45a and45b are provided. The cyclones are connected to a common inlet duct 46which has a top opening 47 positioned to the side of the cyclones 45a,45b. The common air discharge 48 from both cyclones is vertical to aduct 49 open through the inner wall 28 to the space 30 between certainof the I- beams 29. The cyclones are preferably positioned adjacent oneside 50 of the debris box and are supported atop a debris collection bin51 interior of the debris box. An exterior hatch 52 can give access tothe debris collection bin 51. Positioned on the opposite side of thedebris box from the cyclones is an exhaust ducting 55 which is opened tothe spaces 30 and which runs lengthwise of the debris box from a closedend adjacent the rearmost of the spaces 30 communicating to the outlets48 from the cyclones, to the front 31 of the debris box where itconnects with the duct to the primary air flow inducer 16. During normaloperation of the cyclones 45a, 45b, of the debris bin 51, the inlet isclosed from communication with the interior of the debris box 13, exceptthrough the cyclones.

The inlet 47 to the cyclones is closable by a cover 57 attachable acrossthe inlet end 47 of the inlet duct 46. When the cover 57 is positionedatop the inlet 46, 47, the entirety of the cyclones and the debris bin51 are closed from communication with the rear compart ment.

Located in the front compartment 25, is a bag house air filter assembly60. The bag house assembly 60 is suspended from a horizontal wall 61positioned between the transverse wall 33 and the front wall 31 of thedebris box 13 in spaced relation to the inner wall 28 of the debris box13. The horizontal wall 61 has a number of openings therethrough whichcommunicate to the interiors of individual fabric or fabric-like bags 62which depend from the wall 61 into the front compartment 25. The bags 62may be received around wire screens 63 to retain them in place and thebottom ends 64 of the bags are closed. Therefore, all communicationbetween the bottom portion 65 of the front compartment below the wall 61and the top portion 66 above the wall 61, is blocked off, except throughthe fabric of the bags 62 to the interior thereof and thence through theopenings in wall 61.

Portions 28b ofthe inner wall 28 of the top of the debris box 13 areleft open to communicate the space 66 with the spaces between thel-beams 29 in the area of the portions 2812. These spaces 30 are incommunication at one end with the ducting 55.

A high pressure air system is connected to tubing 67 which extends intothe compartment 66 in a plurality of ranks over-lying the openingsthrough the wall 61. Openings 68 in the tubing allow compressed air fromthe tubing 67 to be blasted into the bags 62 through the openings in thewall 61. Valving 68b is provided for each of the ranks of tubing 67extending into the compartment 66. The valvings 68 actuate sequentiallyso that each one of the ranks is subjected to a high pressure air blast,in sequence. In this manner, during the operation of the bag house, whenair is flowing through the bags 62, the sequential blasting of air backinto the bags 62 will shake debris accumulating on the exterior of thebags from the bags in a known manner. The debris separated from the airstream falls to the bottom of the compartment 65 where two transverseaugers 70 extend across the majority of the width of the debris box 13.The transverse augers 70 terminate over the end of a bin-like portion 72extending below the debris box 13, which receives one end 73 of anangled elevating auger 74. The elevating auger 74 extends backwardly andupwardly through an opening 75 in the transverse wall 33. The other end76 of the auger 74 is positioned in the rear compartment 26 adjacent thetop thereof. The auger 74 is surrounded by a tube 77 and terminates in aclosed box 78 having an opening 79 on its bottom side so that the debrismoved from the binlike portion 72 of the front compartment through thetube 77 by the auger is free to drop through the opening 78 at the end76 of the auger into the rear compartment. A closable door or plate 80is provided for the opening 79 so that the enclosure 78 may be closedfrom communication to the rear compartment. By closing the door 80 theentire auger tube 77 is closed from communication to the rearcompartment.

The opening through the interior of the double hull transverse wallbetween the points 38 of the top of the hull 34 and the inner wall 28 ofthe top of the debris box 13 is closable by two or more doors 82, asbest illustrated in FIG. 5. The doors 82 may be attached to the innerwall 28 as by hinges 83 and may be main tainedin a closed position as bya bolt 84. The doors 82 may be rubber-backed as at 85 to maintain atight seal when closed as may be the cover plate or door 80 of theelevating auger 74 and the cover 57 of the opening to the cyclones 45aand 45b.

Operation of the device is as follows:

For collection of the debris where the cyclone air filters are the bestmethod of filtration, the closure door 80 is applied to the opening 79of the auger end housing 78 and the doors 82 are closed to block theopening between the point 38 of the hull 34 and the roof of the debrisbox 13. The closure plate 57 closing the opening to the cyclones isopened. Thereafter, with the compressed air system connected to thetubing 67 being inactive, the primary air flow inducer 16 is activated.This induces an air flow into, and through, the debris box 13 from thedebris collection in end 22 of the hose 15 through the separablecoupling to the inlet 18. The moving air stream, including the debriscollected and to be filtered therefrom, enters the debris box 13 throughthe inlet duct 42 to the rear compartment 26. The majority of the debriswill separate from the air stream in the rear compartment 26. Theremainder of the debris in the air stream will flow through the open ing47 to the cyclone where the remaining debris will be filtered from themoving air stream through the sep arating action of the cyclones in aknown manner. Thereafter, the cleaned air stream passes through theoutlet 48 from the cyclones to the duct 49, then through the openings 30to the outlet duct 55 thence to the primary air flow inducer and theoutlet 98 thereof. The debris separated by the cyclones falls to thedebris bin 51.

When it is desired to operate the system to collect debris best filteredby a bag house, the operation of the system is as follows:

The closure plate 57 is applied to the inlet opening 46 to the cyclonesand the closure plate 80 is removed from the auger end box 78. The doors82 are opened allowing communication from the rear compartment to thefront compartment through the doubled-hulled wall 33. Additionally, thetransverse auger 70 and the angled elevating auger 74 are activated ifdesired. The compressed air source is coupled to the tubing 67 toactivate the air bag cleaning system. Thereafter, the primary air flowinducer 16 is placed in operation to induce the airflow as follows: Airand debris enter the de- I bris collection hose 15 through the open end22 and pass to the interior of the debris collection box through theopening 18 communicating to the inlet conduit 42. The air stream anddebris are passed to the rear compartment 26 where a portion of thedebris will be separated from the air stream falling to the interior ofthe rear compartment. The air stream then passes through the openingbetween the point 38 at the top of the hull 34 and the inner wall 28 ofthe top of the debris box 13. Thereafter, the air flows through thedouble-hulled wall 33 between the beams 36 to the bottom portion 65 ofthe front compartment 25. The air flow will then pass through the fabricbags 62 to the interior thereof then through the openings in the wall61, then through the portions 28a, through the channels 30 and to theoutlet duct 55 and the primary air flow inducer.

The fabric bags 62 will filter the debris remaining in A the air stream.The debris separated from the air stream by the bags will fall to thebottom of the forward compartment 25 where it is directed by angledwalls 88 to the transverse augers 70. The transverse augers 70 will movethe debris to the elevating auger 74 which in turn will move the debristo the rear compartment 26, where it can be removed from the debris box13 by dumping. If desired, an access door 89, illustrated in FIG. 1, canbe provided in the side of the debris box adjacent the ends of thetransverse augers 70 to allow debris removal from the front compartment25 at that point. Additionally, other access doors 90 can be provided tothe interior compartments of the debris box 13 as desired.

It can, therefore, be seen from the above that my invention provides anair filter system for a debris collection apparatus where the air filtersystem consists of two separate air filter systems contained within acommon debris collection box but positioned in separate compartmentswithin the box. Air flow communication is provided between thecompartments when desired and means are further provided closing off oneor the other of the air filtering systems as desired to allow theoperation of the air filtering systems independently and separately ofone another. Additionally, I have provided for removal of debris fromone compartment to the other so as to allow all debris to be dumped fromthe debris collection box from one compartment.

Although the teachings of my invention have herein been discussed withreference to specific theories and embodiments and although illustrativemeans for accomplishing explained results have been described, it is tobe understood that these are by Way of illustration only and that othersmay wish to utilize my invention in different designs or applications.

I claim:

1. A mobile debris collection apparatus comprising:

a'vehicle having a frame;

a debris collection box mounted on said frame;

a debris-laden air inlet to said box;

a clean air outlet from said box;

means exterior to said box inducing an air flow from said inlet to saidoutlet; at least first and second separate and independent airfiltrations systems positioned within said box, said air filtrationsystems being of different types;

means directing the air flow through said box from the inlet to theoutlet through only one of said air filtration systems at a time themeans directing being selectively actuatable to direct the flow throughone of said first and second separate air filtration systems;

the said debris collection box is divided into compartments and one ofthe said air filtration systems is disposed in each of saidcompartments;

a cyclone air filtration system is received in one compartment and a baghouse air filtration system is received in another compartment, thecompartments being separated by a wall, means in the wall comprising apassageway from the one compartment to the another compartment, saidpassageway being closable to close off the compartment containing thebag house air filtration system from the compartment containing thecyclone air filtration system, the air flow through the box from theinlet to the outlet being only through the one compartment when the saidpassageways are closed; and

additional means are provided in said one compart ment to close an inletto the cyclone filtration system whereby air flow through the saiddebris box from the inlet to the outlet is to the said one compartmentthence through the passageways to the said another compartment whenthesaid passageways are open and the said means closing the opening tothe cyclone filtration system are closed.

2. The apparatus of claim 1 wherein the bag house air filtration systemis suspended above the floor of the said another compartment and meansare provided to accumulate debris removed from the air flow by the saidbag house air filtration system adjacent to said floor and additionalmeans are provided to continuously move the said debris collectedadjacent the said floor from the said another compartment to the saidone compartment remote from the bag house whereby the accumulated debrisare removable from the area of the bag house.

3. A mobile debris collection apparatus comprising:

a vehicle having a frame;

a debris collection box mounted on said frame;

a vertical dividing wall mounted in said box and dividing it into firstand second compartments;

a debris-laden air inlet to said first compartment;

21 first air filtration mounted in said first compartment and formedwith a filter passage such that air can pass up through said first airfiltration system from said first compartment;

an air outlet extending to the top of said first air filtration system;

means exterior to said box for inducing air flow from said air outlet;

a first closure means mounted on the top of said first filtration systemto disconnect it from said air outlet;

a second separate and distinct air filtration system of a type differentfrom said first air filtration system mounted in said second compartmentand its outlet communicating with said air outlet;

a second closure means mounted in said vertical dividing wall such thatwhen said second closure means is open and said first closure means isclosed, the debris-laden air passes exclusively through said second airfiltration system, and when said second closure means is closed and saidfirst closure means is opened, the debris-laden air passes exclusivelythrough said first air filtration system.

4. The apparatus of claim 3 wherein said first air filtration system isa cyclone air filtration system and said second air filtration system isa bag house air filtration system.

1. A mobile debris collection apparatus comprising: a vehicle having aframe; a debris collection box mounted on said frame; a debris-laden airinlet to said box; a clean air outlet from said box; means exterior tosaid box inducing an air flow from said inlet to said outlet; at leastfirst and second separate and independent air filtrations systemspositioned within said box, said air filtration systems being ofdifferent types; means directing the air flow through said box from theinlet to the outlet through only one of said air filtration systems at atime the means directing being selectively actuatable to direct the flowthrough one of said first and second separate air filtration systems;the said debris collection box is divided into compartments and one ofthe said air filtration systems is disposed in each of saidcompartments; a cyclone air filtration system is received in onecompartment and a bag house air filtration system is received in anothercompartment, the compartments being separated by a wall, means in thewall comprising a passageway from the one compartment to the anothercompartment, said passageway being closable to close off the compartmentcontaining the bag house air filtration system from the compartmentcontaining the cyclone air filtration system, the air flow through thebox from the inlet to the outlet being only through the one compartmentwhen the said passageways are closed; and additional means are providedin said one compartment to close an inlet to the cyclone filtrationsystem whereby air flow through the said debris box from the inlet tothe outlet is to the said one compartment thence through the passagewaysto the said another compartment when the said passageways are open andthe said means closing the opening to the cyclone filtration system areclosed.
 2. The apparatus of claim 1 wherein the bag house air filtrationsystem is suspended above the floor of the said another compartment andmeans are provided to accumulate debris removed from the air flow by thesaid bag house air filtration system adjacent to said floor andadditional means are provided to continuously move the said debriscollected adjacent the said floor from the said another compartment tothe said one compartment remote from the bag house whereby theaccumulated debris are removable from the area of the bag house.
 3. Amobile debris collection apparatus comprising: a vehicle having a frame;a debris collection box mounted on said frame; a vertical dividing wallmounted in said box and dividing it into first and second compartments;a debris-laden air inlet to said first compartment; a first airfiltration mounted in said first compartment and formed with a filterpassage such that air can pass up through said first air filtrationsystem from said first compartment; an air outlet extending to the topof said first air filtration system; means exterior to said box forinducing air flow from said air outlet; a first closure means mounted onthe top of said first filtration system to disconnect it from said airoutlet; a second separate and distinct air filtration system of a typedifferent from said first air filtration system mounted in said secondcompartment and its outlet communicating with said air outlet; a secondclosure means mounted in said vertical dividing wall such that when saidsecond closure means is open and said first closure means is closed, thedebris-laden air passes exclusively through said second air filtrationsystem, and when said second closure means is closed and said firstclosure means is opened, the debris-laden air passes exclusively throughsaid first air filtration system.
 3. A mobile debris collectionapparatus comprising: a vehicle having a frame; a debris collection boxmounted on said frame; a vertical dividing wall mounted in said box anddividing it into first and second compartments; a debris-laden air inletto said first compartment; a first air filtration mounted in said firstcompartment and formed with a filter passage such that air can pass upthrough said first air filtration system from said first compartment; anair outlet extending to the top of said first air filtration system;means exterior to said box for inducing air flow from said air outlet; afirst closure means mounted on the top of said first filtration systemto disconnect it from said air outlet; a second separate and distinctair filtration system of a type different from said first air filtrationsystem mounted in said second compartment and its outlet communicatingwith said air outlet; a second closure means mounted in said verticaldividing wall such that when said second closure means is open and saidfirst closure means is closed, the debris-laden air passes exclusivelythrough said second air filtration system, and when said second closuremeans is closed and said first closure means is opened, the debris-ladenair passes exclusively through said first air filtration system.